The first Sunday of the NFL season ended with a final flourish of wan incompetence. Eli Manning tossed a useless throw in the direction of Brandon Marshall to the left flat, time running out as the ball bounced near the 30-yard line as the New York Giants trailed, 19-3. Even if Marshall had caught the pointless pass, it would not have counted, because the Giants had not lined up properly and drew a flag.

It marked both a nadir in quality and a fitting cap to Sunday’s offensive ineptitude. All day, teams flailed in attempts to form an offense, and not just those with unproven quarterbacks. Six teams — the Giants, Bengals, Seahawks, Texans, 49ers and Colts — failed to crack double digits in points. It would be fair to give partial credit to good defense. But when teams fail to reach 10 points in fully half of Sunday’s games, it represents an epidemic.

How to explain the terrible offense out of the gate? The concern entering Week 1 centered on a quarterback shortage, and teams that started Scott Tolzien, Tom Savage and Brian Hoyer counted among the offenses unable to manage even a touchdown, extra point and a field goal. But then so did Eli Manning, Russell Wilson and Andy Dalton, two Super Bowl champions and an established starter.

The proper explanation is an intractable issue: NFL football is too dangerous to responsibly prepare for, and the preseason is broken because of it.

Offenses require more full-speed repetition than defenses. Wide receivers and quarterbacks need to hone precision and timing, and offensive lines require cohesion and coordination. Despite an industrial complex of OTAs and minicamps throughout the offseason, the risk of injury and collectively bargained practice constraints deter teams from full-speed, full-contact practices. Preseason games have become a joke, with entire first units playing together for scant reps or not at all.

There’s not a smarter way to do it, either. The risk of injury is too great. The Giants lost Odell Beckham Jr. for Week 1 to a knee injury he suffered in the third preseason game, and his absence turned their attack into a miasma of short passes and hopeless pass blocking. If anything, the Giants would have wished they had played their starters together less in the preseason.

But the effect of properly conserving players for the regular season was evident in Week 1. Offensive lines were especially ill-prepared. The league has an offensive line crisis. Linemen are coming into the league from spread offenses that makes them specialize in short-burst pass blocking, and they do not receive enough full-speed practice to improve technique and coordination. The Giants, 49ers, Seahawks and Colts were the most embarrassing blocking units, but across the league quarterbacks were under extreme duress. It made for ugly football.

It wasn’t just teams with low point totals. The Packers got to 17 points only after cashing in after a turnover inside the Seattle 10, and they have Aaron Rodgers. The Redskins scored just 10 points on offense, needing a pick-six to reach 17.

The problem is, there’s no clear solution. It would be foolish and, in some cases, against CBA rules for NFL coaches to revert to a large slate of full-contact practices or to play starters for longer stretches in preseason games. Players are too big and too fast, and the risks are too steep. There’s not a good way for offenses to prepare for an NFL season. The results showed Sunday.

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